Regulation of Id2 expression by CCAAT/enhancer binding protein β

• Published in: Nucleic acids research Vol. 33; no. 6; pp. 1924 - 1934
• Main Authors: Karaya, Kazuhiro, Mori, Seiichi, Kimoto, Hisashi, Shima, Yoko, Tsuji, Yoshihito, Kurooka, Hisanori, Akira, Shizuo, Yokota, Yoshifumi
• Format: Journal Article
• Language: English
• Published: England Oxford University Press 01.01.2005; Oxford Publishing Limited (England)
• Subjects: Animals; Base Sequence; Binding Sites; CCAAT-Enhancer-Binding Protein-beta - metabolism; Consensus Sequence; DNA-Binding Proteins - biosynthesis; DNA-Binding Proteins - genetics; Female; Inhibitor of Differentiation Protein 2; Mammary Glands, Animal - metabolism; Mice; NIH 3T3 Cells; Pregnancy; Promoter Regions, Genetic; Repressor Proteins - biosynthesis; Repressor Proteins - genetics; Response Elements; Transcription Factors - biosynthesis; Transcription Factors - genetics; Transcriptional Activation
• ISSN: 0305-1048; 1362-4962
• DOI: 10.1093/nar/gki339

Mice deficient for Id2, a negative regulator of basic helix–loop–helix (bHLH) transcription factors, exhibit a defect in lactation due to impaired lobuloalveolar development during pregnancy, similar to the mice lacking the CCAAT enhancer binding protein (C/EBP) β. Here, we show that Id2 is a direct target of C/EBPβ. Translocation of C/EBPβ into the nucleus, which was achieved by using a system utilizing the fusion protein between C/EBPβ and the ligand-binding domain of the human estrogen receptor (C/EBPβ-ERT), demonstrated the rapid induction of endogenous Id2 expression. In reporter assays, transactivation of the Id2 promoter by C/EBPβ was observed and, among three potential C/EBPβ binding sites found in the 2.3 kb Id2 promoter region, the most proximal element was responsible for the transactivation. Electrophoretic mobility shift assay (EMSA) identified this element as a core sequence to which C/EBPβ binds. Chromatin immunoprecipitation (ChIP) furthermore confirmed the presence of C/EBPβ in the Id2 promoter region. Northern blotting showed that Id2 expression in C/EBPβ-deficient mammary glands was reduced at 10 days post coitus (d.p.c.), compared with that in wild-type mammary glands. Thus, our data demonstrate that Id2 is a direct target of C/EBPβ and provide insight into molecular mechanisms underlying mammary gland development during pregnancy.